Powder Coated Aluminium Balustrades Care and Maintenance
1. Outline of the process
2. Introduction
3. General maintenance
4. Restoring weathered, scratched surfaces
5. Anodized Finishes
1. Brief outline of the process:
Aluminium's good resistance to corrosion, and its ability to
develop a natural protective oxide surface film, contribute to
its outstanding properties as a base for organic coatings.
When the metal is properly cleaned, deoxidized where necessary
to remove objectionable residual oxides, then chemically treated
to convert its surface to an inert film, it provides an ideal
substrate for such finishes.
Thorough cleaning of the aluminium surface and its proper chemical
pre-treatment are always of critical importance. The ultimate
performance of any applied coating depends more on the preliminary
preparation and treatment of the metal than on the subsequent
coating application.
In most cases, a five step pre-treatment process is used. Firstly,
a thorough clean and etch is used to remove such contaminants
as coolants, fingerprints and general shop dirt. After the metal
is rinsed, a chromate conversion coating is applied before passing
through two more rinsing processes, the last one having the total
dissolved solids content adequately controlled so no residues
are left on the aluminium.
The metal then passes to the spray booth where banks of electrostatic
spray guns reciprocate the full height of the booth. This ensures
all critical faces and edges have an even coating of powder.
The electrostatic charge serves two purposes:
By charging the powder, it is attracted to the nearest non-charged
surface, this being the object to be coated.
It forces the powder particles to repel each other, similar
to that of poles of a magnet, thus aiding atomization.
The excess powder that has not adhered to the substrate is removed
from the booth by a sophisticated vacuum system. It is then cleaned
and re-used.
The powder coated metal moves out of the booth into the baking
oven where the powder fuses and cures to a durable and flexible
finish.
Powder coating produces colors which are consistent, have an
excellent finish and the system has superb covering characteristics
even on complex shapes such as extrusions.
The powders are available in two grades, depending upon the
application.
Standard polyester powders are the products most commonly used,
with a service life of up to ten years.
High durability polyester powders have higher grade resins and
pigments and offer a service life of up to fifteen years.
2. Introduction
All organic surface coatings, liquid or powder will slowly degrade
in time with the effect of natural weathering. However a powder
coating finish applied to correctly pre-treated metal will offer
excellent adhesion and protection, and if properly maintained
will last several times longer than a standard type of liquid
coating.
One of the reasons for this is that a powder finish is usually
applied at three to four times the thickness of liquid coatings
and is factory baked and cured under controlled conditions. There
are various levels of warrantable coatings which can be offered
to extend the warranty of the application such as 5 and 10 year
high durability applications.
3. General Maintenance of Powder-coated
Aluminium
Cleaning is desirable if the fine finish of powder-coated aluminium
is to be preserved. Deterioration of the coating occurs mainly
as a result of grime deposition and attack by contaminated moisture,
which in a coastal environment contains chlorides and in an industrial
or urban environment contains chlorides and sulfur compounds.
Deposited grime absorbs contaminated moisture like a sponge and
holds it against the powder-coated surface; this permits the attack
to proceed thereby damaging the coating, which cannot be restored
without removal.
Just as the paint work on your car needs regular maintaining
to stay looking in good condition, it is recommended that the
powder coating should also be regularly cleaned to remove air
born deposits such as salt, atmospheric pollution or general dirt.
The powder coated surface must be regularly maintained in accordance
with the powder manufacturer’s data sheets and in areas
where there is a high concentration of salt or atmosphere pollutants
then a systematic maintenance program meeting AMA 610.1 1979 must
be implemented. At the very minimum cleaning should be done at
three to six month intervals (depending on location i.e.. Seaside
or inland, rural or industrial etc.) and is often part of the
regular cleaning program associated with items like the glass
of the Balustrade.
The following procedure should be adopted.
General: Powder-coated Aluminium Balustrades
are delivered to the building site as finished products. Because
of the susceptibility to damage of the powder coating during transportation
and installation, special care is necessary in handling these
products and should not be allowed to rub or slide against each
other during transportation. Powder-coated surfaces should be
well protected during transportation by interleaving or pressure
packing. If contact with unprotected aluminium does occur, that
is, on an uncoated surface, the material should be immediately
washed off with clean water and the surface dried.
Brick Cleaning: Acids used for brick cleaning
can damage the coating and reduce its protective quality. Surfaces
should be protected to prevent contact with brick cleaning acids.
If contact does occur, the surfaces should immediately be thoroughly
washed with copious amounts of clean water.
5. Anodized Finishes
Description of anodizing processes Anodizing produces a high
quality finish which resists corrosion, abrasion and exposure
to industrial, marine and other severe environments. The choice
of either clear or colored anodic films, varying in thickness
from 10 to 25 microns, covers a diverse range of applications.
The client, builder or architect can select the natural lustrous
clear anodized finish or incorporate any of the wide range of
colored finishes. Anodizing is an electrolytic manufacturing process
that makes it possible to build a heavy inert oxide film into
the metal surface.
Aluminium is placed in an electrolyte, (an acid/water solution)
and an electric current passed through the aluminium which becomes
the anode (positive terminal). Under the influence of the electric
current, oxygen forms on this anode and immediately produces a
porous oxide film on the aluminium surface. Extending the duration
of this process increases the thickness of the anodic film.
Once the required thickness of anodic film is obtained, the
aluminium is removed from the electrolyte and "sealed".
Sealing is carried out using hot de-ironised water, steam or room
temperature nickel fluoride solution. A reaction occurs between
the water (or steam) and the porous oxide film. The resultant
film is smooth, hard, homogenous and transparent.
Colors: Clear Anodized is the original process
developed that enhances the surface appearance. Clear anodizing
is often called natural, satin or silver. Light Bronze, Medium
Bronze, Dark Bronze, Matt Black, Bright Silver, Bright Bronze
& Gold, Bright Black, and newer décor colors are available.
High Durability: Ideal for exterior applications
in suburban and rural areas where cleaning is frequent or where
atmospheric conditions are harsh. High Durability has an anodic
film thickness of 10 microns and is available in colors of black,
silver, light, special (standard), medium and dark bronze.
Extended High Durability: A high quality tough
finish developed in strict accordance with AS 1231-1976. Optimum
film hardness is established to ensure extra long life and abrasion
resistance. As color is not dependent on the anodic film thickness,
the most economic film can be specified for the particular application.
Extended High Durability is available in colors of black, silver,
light, special (standard), medium and dark bronze.
The colors for both High Durability and Extended High Durability
are produced by the same electrolytic deposition technique. Stable
inorganic metal/oxide particles are "locked-in" at the
base of the anodic film prior to "sealing".
